When showing films, attempts have frequently been made to give the viewer the impression that he was part of the photographically represented events. Numerous technical solutions have been proposed in view of the attractiveness of a close to reality representation of a generally optically dramatic sequence, such as objects flying towards the viewer, precipitous journeys, etc. These sequences lead to many different reactions on the part of the viewer.
U.S. Pat. No. 4,129,365 describes a wide-angle projection arrangement (Cinerama) in which three projectors project on to a cylindrically curved projection surface a picture formed from three images giving the viewer a panoramic effect. Through the use of a special type of flexible mirror, projection can take place without the viewers seeing the projectors, which projectors are disturbingly positioned below and somewhat in front of the viewers. The necessary transverse magnification of the partial images is produced with anamophotically acting optical means. However, the apparatus cost is considerable for three cameras and two reflecting mirrors for each camera. Special measures are also required to produce an uninterrupted transition between the partial images.
The apparatus expenditure is considerably reduced by the projection arrangement described in U.S. Pat. No. 4,154,514 to Harvey. An image is produced on a projection plane deeply curved in arc-like manner on one side giving the viewer the impression of spatial or three-dimensional action. Projection takes place over an angle between 138.degree. and 153.degree. onto a cylindrically curved plane. Compared with conventional 3D-systems, using an angle of normally less than 90.degree., no additional optical viewing aid is required for producing the three-dimensional impression.
The projection arrangement described in the Harvey patent merely comprises a single projector with anamophotic aids positioned in front of it to produce the necessary very large width/height ratio. Standard 35 mm films with anamorphic images are used for projection purposes.
The optical three-dimensional effect is largely based on the deep curvature of the projection plane, which plane surrounds the viewer of the photographic scene or occupies the viewer's field of the vision such that the picture frame is no longer perceived. Thus, a picture, as perceived by the two eyes with the given interocular distance, is processed by the brain to give a three-dimensional impression.
Another technical solution involves two anamorphotically compressed images correlated with respect to one another with an interocular distance and represented on a standard 70 mm film in a ratio of 1:2. During projection, there is a stereo wide-screen picture effect with two pictures correlated in the interocular distance and defined by different polarization. A viewing aid is provided in the form of a viewer with two polarizers inclined towards one another.
For recording the images two basic optic systems are connected in front of anamorphic attachments, and their optical axes are essentially spaced the average spacing of a pair of human eyes. Since the centre-to-centre spacing of the image on the film is determined by the image format and is generally much smaller than the spacing of the optical axes, the represented object distances are adapted in known manner by reflecting mirrors.
As a function of the conventional anamorphic attachment/basic optics combination, relatively large overall lengths are required, so that the camera angle is limited. The convergence control of the two correlated images is also more difficult for extreme wide-angle projection. The incident light beams of the two optics must be transversely displaced with respect to the optical axes and at the same time focused as soon as the taking distance changes.